Using Preparative tlc. I elute two fractions (Methanolic and Watery) from water extract of tubers of a plant. Both fractions are reddish color but in water fraction there is a small amount of silica gel dissolved. How do I remove it from the water fraction. Thiswater fraction gives single spot on tlc but I am unsure how I crystallized it.
Are you sure it's silica gel contaminating your sample? Remember that people use bare silica for HILIC (aqueous normal phase) HPLC. Prep TLC plates use silicic acid or calcium sulfate as a binder. If your compounds can stand it, make the solution acidic and the silica should precipitate.
Alternatively, pick up the compound in an organic solvent- the stuff from the TLC plate shouldn't dissolve and can be filtered off.
As for crystallizing the compound- sorry- I can't help much. Try picking it up in methanol and letting the methanol evaporate. Maybe try warm dichloromethane.
thanks sir, i will try your suggestion......one more thing can you provide any articles related to Preparative TLC of water extract..............actually i confused about silica gel when i concentrate fraction eluted from water on water bath......then at the bottom white colored silica gel type thing was stands......so i think it may be silica gel.........so if possible please sir clear my confusion????????
Sorry- I don't have a reference for aqueous silica TLC. The binders are generally an issue. I suggest packing a small column with silica and eluting in that fashion. Don't use "Silica G"- this contains around 10% calcium sulfate.
You filter the sample with filter paper, i think that the paper will filter the silica gel or any membrane filter. because before loading into the LC-MS , we need to filter the samples with membrane filter. This is the only way to remove the silica and then you dry the samples with the help of dry bath
ok sir, you mean i should use only silica not silica G in the column and elute this watery fraction.? Are you sure sir after that 10% calcium sulfate separate out. From which mobile phase i elute it and in which ratio?
Sir please give me your email id if u dont mind? i want to be in contact with you regularly.
Try using the same solvents that you used for your prep TLC. Don't use the silica G, just pure silica.
Simply extract that phytochemical in different polar solvent and use whatmann filter papers during filtration to avoid silica. And extraction in different organic solvent with slow evaporation will help you in crystalization. So try it and best of luck
http://orgchem.colorado.edu/Technique/Procedures/Crystallization/Crystallization.html
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